Specific isomerization of rhodopsin-bound 11-cis-retinal to all-trans-retinal under thermal denaturation

Valle, Luís J. del; Ramon, Eva; Bosch, Laia; Manyosa, Joan; Garriga, Pere

doi:10.1007/s00018-003-3113-9

Cited by 11 publications

(19 citation statements)

References 19 publications

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“…This could lead to changes at the tertiary structure level, such as helical translocations, which could be the cause of Rho denaturation (38). This proposal is in agreement with our previous findings concerning thermally induced retinal isomerization (39).…”

Section: Discussionsupporting

confidence: 92%

Salt Effects on the Conformational Stability of the Visual G-Protein-Coupled Receptor Rhodopsin

Reyes‐Alcaraz

Martínez‐Archundia

Ramon

et al. 2011

Biophysical Journal

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Membrane protein stability is a key parameter with important physiological and practical implications. Inorganic salts affect protein stability, but the mechanisms of their interactions with membrane proteins are not completely understood. We have undertaken the study of a prototypical G-protein-coupled receptor, the α-helical membrane protein rhodopsin from vertebrate retina, and explored the effects of inorganic salts on the thermal decay properties of both its inactive and photoactivated states. Under high salt concentrations, rhodopsin significantly increased its activation enthalpy change for thermal bleaching, whereas acid denaturation affected the formation of a denatured loose-bundle state for both the active and inactive conformations. This behavior seems to correlate with changes in protonated Schiff-base hydrolysis. However, chromophore regeneration with the 11-cis-retinal chromophore and MetarhodopsinII decay kinetics were slower only in the presence of sodium chloride, suggesting that in this case, the underlying phenomenon may be linked to the activation of rhodopsin and the retinal release processes. Furthermore, the melting temperature, determined by means of circular dichroism and differential scanning calorimetry measurements, was increased in the presence of high salt concentrations. The observed effects on rhodopsin could indicate that salts favor electrostatic interactions in the retinal binding pocket and indirectly favor hydrophobic interactions at the membrane protein receptor core. These effects can be exploited in applications where the stability of membrane proteins in solution is highly desirable.

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Section: Discussionsupporting

confidence: 92%

Salt Effects on the Conformational Stability of the Visual G-Protein-Coupled Receptor Rhodopsin

Reyes‐Alcaraz

Martínez‐Archundia

Ramon

et al. 2011

Biophysical Journal

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“…Beyond the half life of the thermal decay process (> 30 min), the mean residue ellipticity at 210 nm changes less than 5%, roughly equal to the signal fluctuation in the spectral region, suggesting that changes in secondary structure neither contribute significantly to the thermal decay process nor trigger the thermal isomerization of 11- cis to all- trans retinal. However, it remains possible that the denaturation of rhodopsin could occur at a level beyond secondary structure, such as helical translocations in tertiary structure, to result in compromised thermal stability and function, a notion which aligns with the proposal offered by del Valle et al 9…”

supporting

confidence: 61%

Thermal Decay of Rhodopsin: Role of Hydrogen Bonds in Thermal Isomerization of 11-cis Retinal in the Binding Site and Hydrolysis of Protonated Schiff Base

Liu

Nguyen

et al. 2009

J. Am. Chem. Soc.

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Rhodopsin is a vertebrate dim-light photoreceptor consisting of a seven-helical transmembrane opsin protein and a chromophore, 11-cis retinal, linked to the protein via a protonated Schiff base (PSB). 1 Following photon absorption, 11-cis retinal isomerizes to the all-trans configuration to initiate the visual transduction cascade. Since optimal transduction depends on the thermal stability of rhodopsin, the thermal decay process has long been a subject of interest, yet the chemistry behind it has remained unclear. [2][3][4] Baylor et al. demonstrated that the thermal isomerization of rhodopsin, which enhances dark noise and reduces photosensitivity, generates the same physiological response as photoisomerization. 5,6 Furthermore, rhodopsin was reported to undergo thermal decay characterized by a decrease in visible absorption at 500 nm and an increase in UV absorption at 380 nm upon incubation at 37-55°C. 7,8 The observed thermal decay was attributed to hydrolysis of the PSB. Further analysis by HPLC showed that the concentration of all-trans retinal extracted from rhodopsin increased after incubation in the dark at 55°C. In this case, the thermally-induced isomerization from 11-cis to all-trans was proposed to be initiated by a different process -thermal denaturation. 9 We recently proposed that a hydrogen-bonding network at the retinal binding site 10 is involved in the counterion switch between dark state rhodopsin and metarhodopsin I, an intermediate precursor to transducin photoactivation. 11,12 This theory has prompted our current investigation of the thermal properties of the putative hydrogen-bonding network through solvent deuterium isotope effects. In this report, we attempt to clarify and characterize the chemical reactions responsible for the thermal decay process, with particular emphasis on (1) thermal decay marked by a decrease in optical density at 500 nm (OD 500 ), (2) thermal isomerization of 11-cis to all-trans retinal, and (3) hydrolysis of the PSB. Our results suggest that although PSB hydrolysis and retinal isomerization affect the thermal decay of rhodopsin, denaturation of the secondary structure is not significant. Moreover, we discover that the rates of thermal decay, isomerization, and PSB hydrolysis are two-to three-fold slower in D 2 O than H 2 O. Based on these results, we conclude that the rate-determining step of these thermal processes involves the breaking of hydrogen bonds, which probably stabilize the tertiary structure of rhodopsin, thereby contributing to the high thermal stability.To examine the kinetics of thermal decay, we measured differences in the UV-vis absorption of rhodopsin at appropriate time intervals at 59°C to determine the rates of thermal decay in * elsa.yan@yale.edu.Supporting Information Available: Experimental details (PDF) are available free of charge via the Internet at http://pubs.acs.org. Figure 1A and B). Absorption at 280 nm corresponds to the aromatic amino acids of opsin, while the signal at 500 nm corresponds to rhodopsin with the 11-cis retinal...

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“…1). An interesting point is that the ground state cis molecule is less stable than the trans in isolated conditions, although it has been experimentally shown recently that free 11‐ cis ‐retinal in solution is more stable than expected 5…”

Section: Introductionmentioning

confidence: 99%

Patterns of retinal light absorption related to retinitis pigmentosa mutants from in silico model structures of rhodopsin

Padrón-García¹,

Crespo‐Otero²,

Hernández-Rodríguez³

et al. 2004

Proteins

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Changes induced by mutations in rhodopsin that are associated with the degenerative visual disease retinitis pigmentosa result in an altered pattern of light absorption according to quantum mechanical simulations and reference experimental works. Eleven single-point mutations associated with retinitis pigmentosa at and in the proximity to the retinal binding pocket of rhodopsin have been modeled in silico and their spectra calculated with the NDOL (Neglect of Differential Overlap accounting L azimuthal quantum number) a priori method. The altered pattern of absorption found would lead to cumulative consequences in energy dissipation with aging. Different energy balances in the case of mutants at the very molecular level, compared to native nonmutated rhodopsin, can cause permanent cellular stress and would play a role in the progression of the retine degenerative process. It could explain the worsening of the pathological condition mostly in adults and suggests the probable beneficial effects of using quenching drugs and protection devices against excess of light in the early stages of life for avoiding or reducing potential damage.

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Specific isomerization of rhodopsin-bound 11-cis-retinal to all-trans-retinal under thermal denaturation

Cited by 11 publications

References 19 publications

Salt Effects on the Conformational Stability of the Visual G-Protein-Coupled Receptor Rhodopsin

Salt Effects on the Conformational Stability of the Visual G-Protein-Coupled Receptor Rhodopsin

Thermal Decay of Rhodopsin: Role of Hydrogen Bonds in Thermal Isomerization of 11-cis Retinal in the Binding Site and Hydrolysis of Protonated Schiff Base

Patterns of retinal light absorption related to retinitis pigmentosa mutants from in silico model structures of rhodopsin

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